In northern climes, snow will build up to substantial depths on the roofs of houses in the winter time. Many such roofs are covered with shingles so that the roof is waterproof only when water runs down from the top of the roof toward the eave. Where water builds up in contact with the roof and cannot run off, it seeps up underneath the shingles, and then passes through the roof boards which are not watertight, and passes inside of the house to run down through ceilings and walls to cause extensive damage. The same situation persists where roll roofing is used, the lower edge of each longitudinally extending strip overlying the top edge of the next lower strip of roofing, so that water trapped on the roof can run back up underneath the lower edge of each of the strips having water trapped above it.
In the usual situation, during a less than severe winter, snow will melt and run down over the edge of the roof, and will run off through the gutters, or will freeze to form ice in the gutters, with the melting snowwater running over the edge of the ice and over the gutter and harmlessly off onto the ground.
In severe winters, when the weather is well below freezing on the outside, heat losses from the house, coming up through the roof will tend to cause the snow to melt on the underside and to run down the shingles in the usual manner. When reaching the gutter, the heat from the house is no longer present, and ice will form a dam all along the edges of the roof. This ice dam, whether over a gutter or whether on a roof with no gutter, gradually expands in size as more and more water runs down the roof and tries to get over the top of the dam and onto the ground. As this water gets farther away from the heat leakage source coming up through the house, it drops below freezing and the size of the dam is increased.
It is evident that this "ice dam" action can take place, and often does take place, all the way around the edge of the roof, so that a body of water, under the snow, can exist along the edge of the roof, held in place by the ice dam. This water is free to seep up underneath the shingles and to run down inside of the house. Once inside of the house, it can run along floor joists, around wall plates and down studs, and can seep into ceilings and walls to deface them with water marks if not to actually destroy them by causing them to become loaded with water and to literally fall apart.
During the winter of 1978-1979, it was estimated that over one-third of the houses in the Minneapolis-St. Paul seven county metropolitan area suffered from damage due to the above described ice dam action.
Because of similar damage in previous years, many homeowners have resorted to putting specially made elongated electrical heating elements or cables in their gutters and/or along bottom edges of the roofs where they will be exposed to the snow, and where they can be turned on to remove or prevent any ice dam build-up. This is expensive both in terms of the buying of the heating element originally and in terms of having to supply electrical power to the heating element over large time intervals to prevent ice dam build up. Furthermore, where such elements are not installed before the winter storms, it is not a satisfactory method of removing ice dams once the snow and ice build-up has occurred or once the snow has built up and the ice dam is starting to form.
A common expedient, where physically possible, is to use long handled T-shaped scrapers to scrape the snow above the ice dam down off of the roof and onto the ground (and onto the body of the person holding onto the handle of the scraper, in many cases) in order to let the heat of the sun join with the heat coming up from the house to melt off the ice thus removing the source of the problem of reverse flow of water up through the shingles. This solution is particularly damaging to the roof surface itself, as it presupposes dragging the scraper over the surface of the roof to get the snow down. It is common knowledge that such scraping over a roof surface will tend to knock off the particles on the surface of the shingles thus causing the shingle roof to wear out long before its appointed time. Furthermore, there is a certain amount of physical ability and danger involved in standing on a ladder at the bottom of a slanted roof to manipulate the scraper to cause the snow to come down.
Owners of heavy equipment of the "cherry picker" type have made their equipment and their operators available to clear off roofs. If the operator is careful not to actually touch the roof with his power equipment as he reaches up over the roof and then causes the snow to be carried down from it, this can be effective until such time as the snow falls again. Prices for this kind of work in certain areas of Minneapolis, during the 1978-1979 winter season ranged from $50 to $100 per house, however. Where the conditions for the build-up and formation of ice dams are right, this means virtually $50 to $100 per snow-storm. Obviously this is not a satisfactory alternative except in very extreme cases.
Homeowners have been known to reach out of bedroom windows and gable windows to attack the ice dams with ice choppers and axes and shovels and the like. Cutting a slot through the ice dam is a satisfactory solution as it allows the melted water to all run to the break in the dam and run out over the edge of the roof, and the resulting rather rapid flow of water is often fast enough to drain away the water seeping up under the shingles at least until such time as an ice dam forms again where the break was made. Those in privity with the present applicant can assert, however, that it is all too easy to do accidental damage to the roof, the roofing, and the gutters while using this "main force" approach.
A search was made on this invention in the U.S. Patent and Trademark Office, and two patents somewhat directly related to the problem were located. These are U.S. Pat. No. 3,207,211 granted to Winterfeldt in September of 1965 and U.S. Pat. No. 2,111,251 granted on Spilsbury in March of 1938.
The Winterfeldt patent shows simply the use of relatively small tabs of metal having high heat absorbing and conducting characteristics physically attached below the eaves trough or gutter at intervals. These tabs absorb the heat from the sun or the sky, and tend to keep the water from freezing in the eave trough or gutter. The tabs are fastened to the troughs with hollow rivets so that when ice is melted and water forms in the trough above the tab, the melted water can drip out through the rivet to the ground, thus encouraging the snow and ice in adjacent areas to melt as soon as sufficient heat is transmitted through the gutter from the tab to cause that to happen.
The Spilsbury patent discloses the use of an elongated heating element permanently attached to the eaves or to the gutter to melt or prevent formation of ice in immediate adjacent relationship to metallic flashing along the eaves or the metallic structure of the gutter.
The other patents located in the search which are specifically related to the solar heating of structures were:
U.S. Pat. No. 2,780,415 granted in February of 1957 to Gay; PA1 U.S. Pat. No. 2,998,006 granted in August of 1961 to Johnston; and PA1 U.S. Pat. No. 3,039,453 granted in June of 1962 to Andrassy. PA1 U.S. Pat. No. 3,244,186 granted in April of 1966 to Thomason et al; PA1 U.S. Pat. No. 4,137,901 granted in February of 1979 to Maier et al PA1 U.S. Pat. No. 4,091,798 granted in May of 1978 to Fletcher et al; and PA1 U.S. Pat. No. 4,122,833 granted in October of 1978 to Lovelace.
Gay discloses a heat pump operated system for house heating; Johnston discloses a solar fluid heater related to heating of houses and other enclosures; and Andrassy discloses a heat exchanger unit using solar energy to operate a water heater. None of these patents addresses the problem of elimination or prevention of ice dam build-up. In fact, the conventional roof portions of the structures shown in the Gay and Johnston patents would be subject to ice dam build-up growing out of heat losses straight up through the roof of structures.
U.S. Pat. No. 4,020,605 granted in May of 1977 to Zenos shows the use of panels which can be reversed to absorb heat from the sun in the winter and to reflect heat from the sun in the summer. The invention relates most particularly to flat roof surfaces, and no way in which that structure can be applicable to the present problem is shown or suggested therein.
U.S. Pat. No. 3,001,331 granted in September of 1961 to Brunton shows a roof shingle structure which has surfaces which will be effective to reflect away the high rays of the summer sun and to absorb heat from the low rays of the winter sun. The invention has no relation to the prevention of ice dam build-up even on roofs covered with such shingles and faced with the ice dam build-up conditions as described above.
The remaining patents located in the search made of the prior art are:
All of this last group of patents relate to solar collectors, but none teaches or discloses or even suggests the concept of using such collectors to alleviate or eliminate the problem of ice dam build-up on roofs.
The Thomason et al patent shows the use of transparent or translucent sides of a tent to allow passage of solar rays into the tent to impinge on opaque tent sides thus to heat the tent. It is contemplated that the tent will be turned around in the other direction so that, when the tent is not to be heated, the sun's rays fall on the opaque side of the tent outside of the tent and tend to be reflected.
The Maier et al patent shows the use of a transparent window or pane for allowing solar energy to pass therethrough to reflect on the bottom of a pan of water to bounce up to a reflective sheet and then to reflect back into the water pan. The idea is that the solar energy will be picked up in the water or other liquid as it passes through. Obviously such a structure would not be effective or efficient on a sloping roof where the water in the pan could not lie in a horizontal plane throughout the pan.
The patents to Fletcher et al and Lovelace disclose solar collectors which include right angle triangular pieces of reflective opaque metal which tend to concentrate the sun's rays down on cylindrical tubular receivers where circulating heat transfer liquids carry the released heat to locations for use. These systems are, of course, not passive and require the expenditure of energy to circulate the heat transfer through a medium, for example.
The applicant and those in privity with him know of no closer prior art than that set out above; and they know of no prior art which anticipates the claims made in this application.
In order to provide an effective way to combat ice dam build-up both before it occurs and after it occurs, the structure of the present invention was developed.